Subterranean barriers such as packers normally have a sealing element and one or more assemblies of slips that are urged into contact with a surrounding borehole wall when pushed on ramps referred to as cones. Such barriers can be left in position for a very long time and as result the debris that is in well fluids that can come from the formation or from the borehole wall can over time precipitate down to the set sealing element and the slip assembly that is located above the sealing element. Many releasable packers release with a pickup force that shears a breakable member to allow the assembly of the seal and the slips and associated cones to stretch out. This movement allows the slips to ride down the cones and retract away from a gripping relationship with the surrounding tubular that defines the borehole wall.
To keep parts that need to move with respect to each other clear of debris, packers have been provided with debris barriers that span an annular gap between the packer outer assembly and the surrounding borehole wall. These debris barriers are usually folding structures when viewed in section whose ends are brought together to bring the folds together with the result that the barrier extends radially to span the surrounding gap to the tubular defining the wellbore wall. These devices are deployed after the packer sets and set down weight is applied. One problem with such designs is that due to loading changes or thermal effects that alter the length of the string, the amount of set down weight is variable and can actually disappear. Other designs compress the debris barrier as a result of the same piston movement that sets the slips and seal. However, even in these instances with loading to a predetermined level in a given direction, the compressive force that holds the debris barrier extended can be overcome which leads the barrier to retract and pass debris. This can lead to retraction of the barrier and admission of the debris onto closely fitting relatively moving parts which can then result in their jamming. When that happens the packer may not release and a milling operation could result to get the packer out of the hole. One attempt to address this problem is to unleash the potential energy of a spring against the barrier after the packer is set to help insure that the debris barrier stays folded even when the amount of set down weight on the debris barrier is sharply reduced or eliminated due to thermal effects or other operational reasons. Such a design is shown in U.S. Pat. No. 7,604,048. Fixed dimension debris barriers are shown in U.S. Pat. No. 8,881,802. A weight set debris barrier is shown in U.S. Pat. No. 8,474,522. Axially shifted foam sleeve that are brought into a zone of smaller dimension to span an annular gap are shown in U.S. Pat. No. 8,939,201.
What is needed and provided by the present invention is an articulated debris barrier that is selectively extended to span a surrounding annular gap when a tool such as a packer is set. The extended position of the debris barrier is then releasably locked in when the tool such as a packer is in service. When the tool is released for retrieval the lock on the debris barrier is released so that it can be retracted. This allows the barrier and the tool to be removed without hanging up or damaging the debris barrier. These and other aspects of the present invention will be more readily apparent to those skilled in the art from a review of the description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is to be determined from the appended claims.